Electromagnetic measurements

Electromagnetic compatibility (EMC) has become increasingly important in recent years due to the requirements associated with the implementation, effective January 1, 1996, of the European EMC Directive (89/336/EEC), which was transposed into French law by Decrees 92-587 and 95-283 published in the Official Journal.

This directive was repealed for the first time on July 20, 2007, by Directive 2004/108/EC (transposed by Decree 2006-1278 of October 18, 2006) and then a second time on April 20, 2016, by Directive 2014/30/EU (transposed by Decree 2015-1084 of August 27, 2015).

What is EMC? What implications does the European directive have? It specifies that, to be placed on the European market, equipment must be designed and manufactured in accordance with the state of the art to ensure:

• that the electromagnetic disturbances it generates do not exceed the level beyond which radio and telecommunications equipment or other equipment cannot function as intended;

• a level of immunity to electromagnetic disturbances that can be expected during its intended use, allowing it to function without unacceptable degradation of that use.

With regard to the first condition, the objective is to limit the risk of interference between radio systems (radio transmitters/receivers), to characterize the radio emissions from transmitters and the effects of their radiation, to identify and limit the disruptive potential of non-radio equipment that may interfere with the reception of radio communication systems or disrupt the operation of other nearby equipment, to ensure the cleanliness of 50 Hz power supply signals by limiting the amplitude of 50 Hz harmonics fed back into power grids and all associated signals, and to prevent signals from powerful radio communications or broadcasting transmitters from coupling through telecommunications or power grids, etc.

The second condition necessitates identifying, characterizing, and therefore measuring the disturbances emitted by devices, as well as the disturbances that may affect them.

The purpose of this article is therefore to characterize electromagnetic compatibility (EMC) measurement methods in both directions: disturbances generated by equipment and disturbances affecting equipment. This article will refer only to harmonized standards in the civilian sector (CENELEC, IEC, and CISPR) and will not cover measurement methods developed within the framework of military, aeronautical, or automotive specifications. However, many of the methods used by military authorities—which are based on signals of the same nature to be measured—turn out to be similar in principle, although not identical in test methodology or measurement interpretation.